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The Doomsday Clock was moved 30 seconds closer to midnight on Thursday, as the Bulletin of the Atomic Scientists said reckless language over nuclear weapons and a growing disregard of scientific expertise on climate change put humanity in its greatest peril for more than 50 years. Now at two and a half minutes to midnight, the clock is the closest to midnight since 1953 when the U.S. and the Soviet Union both tested hydrogen bombs. (Published Thursday, Jan. 26, 2017)

The Doomsday clock has ticked 30 seconds closer to apocalyptic midnight, and the scientists who control it are laying some blame at the feet of President Donald Trump.

The Bulletin of the Atomic Scientists moved the hands of the clock, a symbolic countdown to the world's end, to two-and-a-half minutes to midnight Thursday. It's the closest the clock has been to midnight since the 1950s, when the country was in the midst of the Cold War.

The Bulletin noted a darkening international security landscape featuring rising nationalism and the United States and Russia at odds in several regional conflicts. Scientists expressed concern about Trump's refusal to take climate change more seriously — he's skeptical of the scientific consensus on climate change — and his "disturbing" nuclear rhetoric.

Trump refused during the campaign for president to rule out using nuclear weapons and in December said the U.S. must increase its nuclear arsenal.

Trump, Putin Raise Fears of Nuclear Arms Race

President-elect Donald Trump vowed to enhance America's nuclear capabilities, warning Russian President Vladimir Putin Friday to avoid circumstances that may set the two global powers on an "alternate path." NBC’s Jennifer Johnson reports.

(Published Friday, Dec. 23, 2016)

"To step back further from the brink will require leaders who have both vision and restraint. President Trump and [Russian President Vladimir] Putin, who claim great respect for each other, can choose to act together as statesmen, or act as petulant children," said Lawrence Krauss, director of the Bulletin's Board of Sponsors.

The Doomsday Clock was created 70 years ago. This is the first time the scientists behind it have moved it 30 seconds, which reflects the fact that Trump has only just taken office.

"Even though he has just now taken office, the president's intemperate statements, lack of openness to expert advice, and questionable cabinet nominations have already made a bad international security situation worse," the Bulletin said in a statement.